diff --git a/Number_types/include/CGAL/Sqrt_extension/Eigen_NumTraits.h b/Number_types/include/CGAL/Sqrt_extension/Eigen_NumTraits.h
index b51e888839a..5725578ec46 100644
--- a/Number_types/include/CGAL/Sqrt_extension/Eigen_NumTraits.h
+++ b/Number_types/include/CGAL/Sqrt_extension/Eigen_NumTraits.h
@@ -14,10 +14,15 @@
 #ifndef CGAL_SQRT_EXTENSION_EIGEN_NUMTRAITS_H
 #define CGAL_SQRT_EXTENSION_EIGEN_NUMTRAITS_H
 
+#ifdef CGAL_EIGEN3_ENABLED
+
+#include <Eigen/src/Core/NumTraits.h>
+
 namespace Eigen {
   template<class> struct NumTraits;
   template <class NT,class ROOT, class ACDE_TAG, class FP_TAG>
   struct NumTraits<CGAL::Sqrt_extension<NT, ROOT, ACDE_TAG, FP_TAG> >
+    : GenericNumTraits<CGAL::Sqrt_extension<NT, ROOT, ACDE_TAG, FP_TAG> >
   {
     typedef CGAL::Sqrt_extension<NT, ROOT, ACDE_TAG, FP_TAG> Real;
     typedef Real NonInteger;
@@ -38,4 +43,6 @@ namespace Eigen {
   };
 }
 
+#endif // CGAL_EIGEN3_ENABLED
+
 #endif